Generally, for transmission/reception of data on network, a connection can be set up between a UE and an eNB. That is, the eNB can allocate a radio resource to the UE for communicating with the UE.
An eNB supporting a long term evolution (LTE) communication scheme which follows an LTE standard can use a RRC protocol in order to allocate a radio resource to a UE. That is, the eNB can allocate a radio resource to each of UEs which need a communication using the RRC protocol, and can release radio resources which are allocated to UEs which do not communicate among the UEs which are allocated the radio resources. The RRC protocol can be a protocol used for managing radio resources which will be allocated to UEs within a cell.
In the RRC protocol, a state of a UE can be classified into two states: a RRC_IDLE state and a RRC_CONNECTED state. Each of the RRC_IDLE state and the RRC_CONNECTED state will be descried below.
The RRC_IDLE state can be a state in which a UE is not allocated a radio resource from an eNB or a RRC connection between the UE and the eNB is released.
The RRC_CONNECTED state can be a state in which a UE can transmit/receive data to/from in a downlink (DL) or uplink (UL) after being allocated a radio resource form an eNB.
Recently, smart phones can be populated, so various applications such as a social network service (SNS), an instant messenger (IM) service, a voice over internet protocol (VoIP) service, a mail client, and the like are widely used. Most of these applications can run based on a push service or a polling service. For this, each of the applications periodically can transmit a keep alive message to an application server, or periodically receive a polling message from the application server in order to update data.
A size of the keep alive message or the polling message can be generally small (such as less than 1 KB), but the keep alive message or the polling message can be frequently transmitted. Messages used for transmitting/receiving non-user data which have relatively a small size and are frequently transmitted can be called “background control traffic”, and can have the following characteristics.
Firstly, the background control traffic can be mostly transmitted by a UE. That is, applications which are installed in the UE can transmit the background control traffic for operating the applications.
Secondly, the background control traffic can be transmitted regardless of user interaction. That is, the background control traffic can be transmitted without the user interaction such as a key input, a screen touch input, and a sound input from the user, or the like. Even though a screen of a smart phone is turned off, the background control traffic can be transmitted.
Thirdly, transmission of the background control traffic can be completed within a relative short time. That is, the background control traffic can consist of a few or dozens of packets, and the background control traffic can be relatively rapidly transmitted. Further, transmission of the background control traffic can be completed within few seconds, and there can be no traffic following the background control traffic.
Fourthly, the background control traffic can periodically occur. Each application can have a period for transmitting its background control traffic, and the period for transmitting the background control traffic can be variously set.
Lastly, the background control traffic can occur all day long. That is, each of the applications can continuously transmit its background control traffic to a related server in the middle of the night such as when a user sleeps. So, the background control traffic can occur with various periods all day long. This means that a UE can operate in the RRC_CONNECTED state during a relatively long time, and battery life time can severely decreases due to this. So, the decrease of the battery life time can result in a grave inconvenience to the user.